This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. HIV is a sexually transmitted disease and a vaccine capable of preventing sexual transmission of HIV should elicit mucosal immune responses in the genital tract. The objectives of this study were to determine which immune responses confer protection from intravaginal challenge with SIVmac 239.